BENEFITS AND DRAWBACKS OF PODDED PROPULSION

December 11, 2018

BENEFITS AND DRAWBACKS OF PODDED PROPULSION

There’s a good chance that any icebreakers or large cruise ships built in the last 20 years use a podded propulsion system.

The design, which has a motor mounted inside a “pod,” replaces a conventional ship propeller and rudder. It offers good maneuverability and better fuel efficiency, and has become popular with ships ranging from yachts to oil tankers and cruise ships.

For marine pilots, the gearless podded-propulsion vessels have different handling characteristics than traditional ships that use rudders to assist in steering. Resolve Maritime Academy offers a two-day podded propulsion course for licensed marine pilots to boost their proficiency and confidence while handling these vessels. Enrollees will have the chance to use Resolve’s full-bridge and mini-bridge simulators to experience maneuvers such as docking, undocking, and transiting channels with different pod configurations. The course also includes videos to supplement lectures to explain the history, benefits, and shortcomings of podded propulsion.

The instructors for this class are licensed pilots with years of experiencing maneuvering some of the largest podded passenger ships in the world.

Resolve Maritime Academy also offers a five-day advanced ship-handling course for large podded vessels. This customizable class makes extensive use of Resolve’s simulators to teach the complex operations necessary with such vessels. It covers docking/undocking, avoiding collisions, partial or complete propulsion loss, handling high winds or currents, anchoring and emergency maneuvers.

The technology that led to the creation of podded propulsion was jointly developed by two European companies in the late 1980s. Swiss electrical equipment manufacturer ABB Group and Finnish shipbuilder Masa-Yards worked to design a new type of electric ship propulsion.

Unlike conventional azimuth thrusters, which have an engine inside a ship’s hull to power the propeller, the design ABB and Masa-Yards came up with mounted an electric motor inside the propulsion unit, connecting the propeller to the motor shaft. The unit has the ability to rotate 360 degrees, providing thrust in any direction. The design pulls a ship through the water instead of pushing it, which greatly enhances maneuverability and improves fuel efficiency.

The first prototype was installed in 1990 on an icebreaker docked in Helsinki. The design, later called an “Azipod,” substantially improved the ship’s icebreaking abilities and allowed it to break up ice whether moving forward or backward.

The Azipod was considered so revolutionary that when the original was uninstalled in the early 2000s it was put on display at a maritime museum in Turku, Finland.

CRUISE INDUSTRY INTEREST

Podded-propulsion units were soon added to oil tankers and by the late 1990s, cruise ships. Carnival Cruise Line’s Elation, a $300 million, 72,000-ton ship christened in 1998, was the first cruise ship to be outfitted with the Azipod system. In the case of the Elation, the ship uses two 14-megawatt pod-propulsion units. The technology soon spread to other ships, and today, the cruise industry is among the largest users of podded-propulsion vessels.

Similar designs have been introduced by competing engine manufacturers such as Rolls-Royce.

As popular as podded propulsion designs are, the configuration does come with some drawbacks. The cost of a podded propulsion system is generally higher than a conventional design, and the propulsion efficiency is a little less. Installation requires a redesign of the ship’s stern. For pilots, the steering of a pod-propulsion vessel is substantially different than a conventional vessel, and special training is required.

Despite those disadvantages, pod propulsion has continued to grow in popularity and numerous configurations are available today. The technology is credited with saving more than 700,000 tons of fuel and reducing the maritime industry’s carbon footprint.